In a hybrid vehicle and an electric highway vehicle voltages are used that are greater than 60 V DC. These voltages are designated as being high voltage in the vehicle, and they are the cause of dangerous leakage currents. The high voltage network, also called DC voltage intermediate circuit, in a hybrid vehicle and an electric highway vehicle, in the simplest case is made up of a battery, a voltage inverter having a DC voltage intermediate circuit capacitor, and one or more electric machines, additional high voltage consumers such as an electric climate control compressor and a cable harness which connects all the high voltage components to one another. The voltage inverter requires a DC voltage intermediate circuit capacitor for its functioning, having a sufficiently great capacitance. When switching the high voltage battery into the high voltage network, to which the DC voltage intermediate circuit capacitor is also connected, in order to avoid a short circuit current or an overcurrent, the DC voltage intermediate circuit capacitor is charged via a precharging resistor, which is usually located in the battery. After the expiration of the precharging time for the DC voltage intermediate circuit, the actual main contactor is closed and the precharging resistor is bridged. After the switching off of the high-voltage system, for instance, by disconnecting the high-voltage battery from the high-voltage network, all capacitors that are connected to the DC voltage intermediate circuit have to be discharged. For this purpose, a separate discharge circuit is normally used—in the simplest case an ohmic discharge resistor, which is permanently connected in parallel to the intermediate circuit capacitor.
An apparatus for the rapid discharge if an intermediate circuit capacitor, that is at a higher voltage, is described in German Patent Application No. DE 10 2004 057 693 A1. In this design approach, a DC voltage converter is used, in which the low-voltage-side voltage is increased so as to decrease the voltage peaks. In order to decrease the voltage peaks, on the battery side, a resistor is connected between the DC converter and ground, by a switch.